C++ OIS Segfault When Almost Identical Functions Work

Question

See important edit below!

Hi all I'm having trouble figuring out why this segfault is happening. I'm using the Ogre and OIS library. Here is the code that causes it:

bool Troll::Application::keyPressed(const OIS::KeyEvent& event) {
    //TODO: Segfault here!
    Troll::State* state = mStateManager->peek();
    state->key_pressed(event); //This causes the SEGFAULT!!!
    return true;
};

And the key_pressed function:

void Troll::RootState::key_pressed(const OIS::KeyEvent& event) {
    std::cout << "You got here" << std::endl; //this isnt printed!
    std::cout << "Key Pressed: " << event.key << std::endl;
};

Because the segfault is happening on key_pressed but the first line of key_pressed isn't being executed, I can only guess that it is passing the const OIS::KeyEvent& that is causing it.

And the weird thing about this is I have three other functions that are almost identical (but for the mouse) which work perfectly.

bool Troll::Application::mouseMoved(const OIS::MouseEvent& event) {
    mStateManager->peek()->mouse_moved(event);
    return true;
};
void Troll::RootState::mouse_moved(const OIS::MouseEvent& event) {
    std::cout << "Mouse Moved: rel x = " << event.state.X.rel << std::endl;
    std::cout << "             rel y = " << event.state.Y.rel << std::endl;
    std::cout << "             abs x = " << event.state.X.abs << std::endl;
    std::cout << "             abs y = " << event.state.Y.abs << std::endl;
};

I'm creating a basic state system so I can start writing applications for Ogre3D using the OIS library for input. I have an Application class which acts as an input listener for the mouse and keyboard. Here is how its setup...

void Troll::Application::setup_ois() {
    //create a parameter list for holding the window handle data
    OIS::ParamList pl;
    size_t windowHnd = 0;
    //we need the window handle to setup OIS
    std::ostringstream windowHndStr;
    mWindow->getCustomAttribute("WINDOW", &windowHnd);
    windowHndStr << windowHnd;
    //add the handle data into the parameter list
    pl.insert(std::make_pair(std::string("WINDOW"), windowHndStr.str()));
    //create the input system with the parameter list (containing handle data)
    mInputManager = OIS::InputManager::createInputSystem(pl);
    //true in createInputObject means we want buffered input
    mKeyboard = static_cast<OIS::Keyboard*>(mInputManager->createInputObject( OIS::OISKeyboard, true ));
    mMouse = static_cast<OIS::Mouse*>(mInputManager->createInputObject( OIS::OISMouse, true ));
    //set this as an event handler
    mKeyboard->setEventCallback(this);
    mMouse->setEventCallback(this);
};

The application class relays the mouse moves, button pressed and key strokes to the Troll::State (the framework I'm making is called Troll) at the top of the state stack which is inside the Troll:: StateManager (which is merely a wrapper for an std::stack with memory allocation and startup() and shutdown() calls)

Sorry for any confusion the difference of the naming conventions causes for some reason I decided to use_underscores_for_some_reason and I haven't got round to changing it. Thanks in advance, ell. Hope you can solve my problem and please inform me if I haven't given enough detail.

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EDIT: After recently upgrading to Ubuntu Natty Narwhal I cannot get the debugger to work properly, it just crashes the computer. I use Code::Blocks and I don't have a clue how to use a debugger or compiler outside the IDE (sad I know, but I'll get round to learning someday). So sorry, I can't use a debugger.

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EDIT: In response to GMan's comment, even if I check for null, I still get segfaults

bool Troll::Application::keyPressed(const OIS::KeyEvent& event) {
    //TODO: Segfault here!
    Troll::State* state = mStateManager->peek();
    if(state == 0) {
        std::cout << "State is null!" << std::endl;
    };
    state->key_pressed(event);
    return true;
};

Although I'm not sure thats the correct way to check for null? Also, other methods using peek() work correctly. Thanks again! :)

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Important Edit: It seems that it is in fact the peek function that is causing trouble, but only when called from the keyPressed function. I discovered this by adding a parameter to peek() so that it would print the address of the state object it return as well as the message. By setting the message parameter to the function from where the peek() function is called, I got these results.

Root state is: 0x8fdd470
Peeking state... 0x8fdd470 from: Application::frameRenderingQueued()
Peeking state... 0x8fdd470 from: Application::mouseMoved
Peeking state... 0x8fdd470 from: Application::frameRenderingQueued()
Peeking state... 0x8fdd470 from: Application::frameRenderingQueued()
Peeking state... 0x8fdd470 from: Application::frameRenderingQueued()
Peeking state... 0x936cf88 from: Application::keyPressed
Segmentation fault

Notice that when the keyPressed function calls the peek method, a different address is shown. I cannot see why a different address is being returned only when the keyPress function calls peek? Somebody please help me with this!

Answer 1

What happens when you check for mStateManager being NULL, and for NULL being returned from mStateManager->peek()?

bool Troll::Application::keyPressed(const OIS::KeyEvent& event) {
    if (mStateManager == NULL) {
        //! set breakpoint on next line
        std::cout << "mStateManager is NULL, returning false" << std::endl; 
        return false;
    }
    std::cout << "about to call peek" << std::endl;
    if (Troll::State* state = mStateManager->peek())
    {
        std::cout << "about to call key_pressed" << std::endl;
        state->key_pressed(event); //Does this still cause a SEGFAULT?
        std::cout << "back from key_pressed" << std::endl;
        return true;
    }
    std::cout << "mStateManager->peek() returned NULL, returning false" << std::endl; 
    return false;
};

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EDIT: I edited the code to print each branch, how it was traced through.